The erosion of soil on the earth continues to occur as rain and flood waters run from high elevations to lower elevations. Many efforts have been made to reduce the erosion of soil by interrupting the runoff of water, or at least slow down the water flow and thereby reduce the extent of erosion. Erosion control blocks are available for covering watershed areas to protect the underlying soil from being carried with the runoff water. Many styles, shapes and sizes of erosion control blocks are available for placement together to form a mat that covers the ground to be protected from erosion. The use of erosion control blocks is preferred over the use of a slab of concrete, as concrete can crack and settle if the underlying ground is unstable, which it is in many watershed areas. It is also difficult to make a concrete slab that is adapted to slow down the velocity of water that flows thereover. Erosion control blocks of the articulating type continue to conform to the contour of the ground, even when the ground contour changes.
Blocks that are simply placed side by side on the ground are helpful in reducing soil erosion, but only in situations where the velocity of the runoff water is low or moderate. Otherwise, the hydraulic lift of the flowing water can cause the blocks to actually lift off the ground and be carried or otherwise moved so that the erosion protection is compromised. Of course, the heavier the block the less likely it is to be moved by high velocity water currents. This solution is costly and often prevents the installation of the heavy blocks by persons who must lift each block and place it into position with others to form the mat.
More recently, erosion control blocks have been constructed so as to be laterally interlocking so that horizontal movement is prevented. U.S. Pat. No. 5,556,228 by Smith is an example of a commercially accepted interlocking erosion control block that articulates to conform to the contour of the ground. Such type of block has been accepted by governmental organizations for use on large waterways to halt erosion of the same. Disclosed in U.S. Pat. No. 5,020,938 by Scales is a revetment block that employs a number of cavities and a number of tongues that engage the respective tongues and cavities of neighbor blocks to form a mat. While this arrangement provides some degree of vertical interlocking, the blocks can be freely removed from each other in a lateral direction. The hydraulic stability of such type of block is compromised.
From the foregoing, it can be seen that a need exists for an erosion control block that is both horizontally interlocking as well as vertically interlocking. Another need exists for an erosion control blocks in which a portion of the neighbor blocks overlie each block and prevent hydraulic forces from lifting the block, which otherwise might be displaced by high velocity flood waters. Yet another need exists for erosion control blocks which, when interlocked together, form an interlocking mat that dissipates the energy of the water flowing thereover.